Formal:
* बहुत अच्छा कहा (bahut achchha kaha) - This is a very common and versatile phrase, literally meaning "very well said."
* आपने बिलकुल सही कहा (aapne bilkul sahi kaha) - This means "you said exactly right."
Informal:
* बिलकुल सही (bilkul sahi) - This is a shorter and more casual way of saying "exactly right."
* वाह! (vaaah!) - This is a more enthusiastic way of saying "well said," similar to "wow!"
More specific phrases:
* आपकी बात बिलकुल सच है (aapki baat bilkul sach hai) - This means "what you said is absolutely true."
* मुझे आपकी बात से सहमति है (mujhe aapki baat se sahmati hai) - This means "I agree with what you said."
The best phrase to use will depend on the specific situation and your relationship with the person you are speaking to.